Environmental Concerns and the State of the Aquatic Environment
Availability of water resources for the fisheries of the Lower Don River
Zhukova S.V.
Abstract. The Lower Don fishing area is of crucial importance for the reproduction of fish stocks in the Azov Sea, as the spawning grounds of valuable anadromous and semi-anadromous fish species are located in the section of the Don River from the Tsimlyansk Reservoir to its estuary. One of the main reasons for the catastrophic decline in the fish productivity of the Azov Sea is irregularity of spring flooding of the floodplains, on which the spawning grounds of sturgeon fish species, bream, zander, roach, vimba bream, shemaya, herring and other fish species of commercial importance are historically located. The water supply of the Lower Don under the conditions of anthropogenic and climatic transformations of the Don River flow was analyzed; causes of disruption of the natural reproduction processes for anadromous and semi-anadromous fish species were identified. Analysis of the structure of natural and regulated runoff of the Don River, for which the data, collected during long-term observations at the hydrological station in the Don River (Razdorskaya Settlement) were used for the period from 1912 to 2018. Grapho-analytical and mathematical statistical methods of analysis for the hydrological data series were applied. The reasons for disruption of the processes of natural reproduction are indicated, and the periods when the regime of floodplain flooding facilitated the effective spawning of fish are identified; the years, when it was not possible to accomplish ecological and fishery augmentations (water releases from the Tsimlyansk Reservoir), have been established as well. A set of measures to restore impaired fisheries capacity of the Lower Don Basin and the Azov Sea is proposed.
Keywords: Don River, river runoff, spawning grounds, flow regulation, discharge hydrographs, ecological and fishery flow augmentations
Biology and Ecology of Aquatic Organisms
Assessment of abundance and biomass of the European anchovy (Engraulis encrasicolus) breeders in the North-Eastern Black Sea based on the data from ichthyoplankton surveys
Nadolinskiy V.P., Nadolinskiy R.V.
Abstract. Estimation of changes in abundance and biomass of the European anchovy breeders along the Caucasian coast of the Black Sea is made. Ichthyoplankton surveys have been applied as the main research method. The samples were collected with the ichthyoplankton conical net during the mass spawning of the thermophile marine fish species in the Black Sea (May–September). Trawling was conducted in the upper water layers; half a diameter of the net was immersed. It has been found out that, in summer, European anchovy is widely distributed over its whole habitat and keeps to the upper water layers above the layer of thermocline. In the North-Eastern Black Sea, first anchovy eggs occur in ichthyoplankton catches in May, and the spawning season ends in September. The peak of spawning falls on the summer months. Based on the data of ichthyoplankton net catches, it is characteristic for anchovy eggs to prevail in the layer above 20 m depth or more during the entire spawning season; by contrast, early larvae are most often recorded in the coastal waters and shallow waters of the shelf above the depth up to 50 m. According to the estimations, in total, from 14 to 380 million European anchovy breeders were distributed over the shelf of the North-Eastern Black Sea in the summer seasons of 2001–2018; their biomass amounted to 100–3000 t.
Keywords: European anchovy, eggs, early juveniles, North-Eastern Black Sea, breeders, abundance, biomass
Limiting factors of the abiotic environment and biological characteristics
of important commercial migratory fish species of the Azov Sea
Cherednikov S.Yu., Vlasenko E.S., Zherdev N.A., Kuznetsova I.D., Lukyanov S.V.
Abstract. The data, collected from different sources, are referred to the limiting factors of the aquatic environment (temperature and salinity effects, oxygen regime, water flow speed) and biological characteristics of the most commercially important anadromous and semi-anadromous fish species of the Azov Sea, such as zander Sander lucioperca (Linnaeus, 1758), common roach Rutilus rutilus (Linnaeus, 1758), common bream Abramis brama (Linnaeus, 1758), vimba bream Vimba vimba (Linnaeus, 1758), the Prussian carp Carassius gibelio (Bloch, 1782), and the Pontic shad Alosa immaculata (Bennett, 1835). Data on fertility, age of maturation, incubation time and feeding of these species in the Azov Sea environment are also presented. The material is based on the literature sources, long-term observations, and monitoring studies. Analysis of the available data has made it possible to identify upper and lower temperature limits for the listed fish species, to compare the temperature at the beginning of their spawning and their thermal optimum for spawning, to provide insight into the specificity of their salinity resistance and optimal oxygen content, to collate characteristic features of the reproductive cycle of different fish species, to compare their movement speed, and to find dissimilarities in their feeding preferences.
Keywords: Azov Sea, commercial species, anadromous fish species, semi-anadromous fish species, temperature, salinity effects, oxygen regime, fertility, age at maturity, feeding, incubation period, ontogenesis, pelagic zone, benthos
Distribution of the juveniles of common roach Rutilus rutilus, common bream Abramis brama, vimba bream Vimba vimba, and zander Sander lucioperca in the Lower Don in low-water year of 2017
Zherdev N.A., Vlasenko E.S., Guskova O.S.
Abstract. When the Tsimlyansk Hydrounit had been put into operation, it introduced changes in the distribution of the intra-annual runoff of the Lower Don River, which meant partial or full accumulation of spring floods and an increase in expenses during the summer-autumn and winter low-water period (baseflow). The major bulk of the accumulated water was utilized for shipping and agriculture. With this mode of operation of the Tsimlyansk Hydrounit, spring flooding of the floodplain did not occur in the low-water year of 2017. The studies on the distribution of juveniles of common roach, common bream, vimba bream, and zander were carried out in May– September, 2017 at the Lower Don area, from the Kochetovsky Lock to the mouth. As a fishing gear, a 32-meter fry dragnet was used for catching the juveniles in the coastal zone. The location of the stations was selected taking into account availability of suitable sites for dragnet hauls. In the dragnet catches, 35 species belonging to nine families were recorded. In the low-water year of 2017, juveniles of low-value fish species prevailed in the ichthyocenosis composition (86.86 %), whereas juveniles of valuable fish species accounted for only 13.14 %. Among valuable fish species in the ichthyocenosis composition, roach juveniles were more abundant than those of the bream and vimba bream. The share of zander juveniles was insignificant. The juveniles of roach, bream, vimba bream and zander confined themselves to sparse macrophyte beds, covering a significant area of coastal shallow waters, and to the river estuaries flowing into the Lower Don River In the low-water year of 2017, the downstream migration of juvenile roach, bream and zander began in June, while for the vimba bream yearlings it began in late May. During their downstream migration, juveniles stick to coastal shallow waters overgrown with macrophytes and to the estuarine parts of the rivers flowing into the Don River. From June to September, migrating juveniles of roach, bream, vimba bream and zander accumulated in the middle part, where they were feeding and fattening for some time, and then migrated further downstream. An analysis of the data collected during the field studies allowed to assess the generation of roach, bream, vimba bream, and zander born in 2017. It has been evaluated as low-yield.
Keywords: Rutilus rutilus, Abramis brama, Vimba vimba, Sander lucioperca, Lower Don River, abundance, distribution, downstream migration
Current state of zooplankton in Lake Urozero (the Republic of Karelia)
Fomina Yu.Yu., Syarki M.T.
Abstract. Lake Urozero is a state regional hydrological natural monument of the Republic of Karelia. This water body is characterized by high transparency and high water quality. During the recent decades, climatic changes and fluctuations in temperature and precipitation have been observed in the investigated area, all of which may affect the state of aquatic ecosystems. The modern state of zooplankton in the pelagic zone of Lake Urozero has been assessed based on the observations, carried out in May, July and September, 2018. Catches were extracted using the net method at a deepwater station in the center of the lake. In the pelagic zone of the lake, 25 species and groups were identified up to the genus and lower (8 species of copepods, 8 species of cladocerans, and nine species of rotifers). The species composition and dominant complex of the zooplankton community was stable and has not changed since the 1950s. Seasonal changes in the community correspond to the regularities typical for the lakes of Karelia. The vertical distribution of zooplankton has some specific features, stemming from high transparency of the water. During the growing season, most organisms are concentrated below 10 m due to the distribution of food resources and/or the influence of planktonophagous fish species. Summer values of the abundance (27,350 ind./m3) and biomass (0.906 g/m3), as well as functional (production of 57 kcal/m2 per season) zooplankton indicators of Lake Urozero correspond to the oligotrophic status of the plankton system.
Keywords: seasonal dynamics, biodiversity, biotic balance, transparency, vertical distribution, zooplankton
Zooplankton of the Chogray Reservoir in the present period
Kornienko G.S., Chayka T.V.
Abstract. This paper provides the information on the quantitative development and species diversity of the zooplankton community in the Chogray Reservoir for 2018, and the data on long-term changes in zooplankton abundance and biomass for two seasons (spring and autumn). The literature data on these issues from the moment of filling the Chogray Reservoir with water and in the subsequent years are presented as well. The analysis of changes in species diversity and quantitative development over the past 40 years is given. Dominant groups of zooplankters and dominant species among them are identified. A comparison of the dynamics of taxonomic and quantitative development of the zooplankton in the Chogray Reservoir has shown that, over the past 40 years (from 1978 to 2018), its species composition has changed qualitatively. The number of species of planktonic organisms has doubled, mainly on account of rotifers and copepods. The plankton species abundance in 2018 is slightly higher than during the period of filling the reservoir with water in 1971 (25 and 20 species, respectively). At the present time, the copepods prevailed in the plankton, accounting for up to 74.7 % of the abundance and 82.0 % of the total biomass. Average values of the abundance of zooplanktonic organisms do not vary significantly between years during the investigated 40-year period, but, on the average, their biomass was 4 times higher in 1977–1978, mainly on account of the development of larger forms of cladocerans and copepods. The average zooplankton biomass in the Chogray Reservoir is 0.3–0.5 g·m-3, which corresponds to the biomass of mesotrophic reservoirs. It is concluded that the natural food resources for fish farming in the Chogray Reservoir have been preserved.
Keywords: Chogray Reservoir, zooplankton, biomass, abundance, species diversity
Characterization of the zooplankton species composition in the Lower Don
Shlyakhova N.A.
Abstract. In this paper, the data on zooplankton species composition of the Lower Don are presented for the vegetation periods of 2016–2018 in the context of seasonal changes (spring, summer and autumn). Literature data on species composition of the zooplankton community are given for the years before the Don River had been regulated, and for the subsequent decades. Long-term changes in species composition of the zooplankton community have been analyzed. Based on the conducted studies, dominant groups of zooplankton have been identified, as well as dominant species among them. Thus, in the spring seasons, rotifers were the most abundant and dominant zooplankton group; in the summer seasons, cladocerans and copepods prevailed in nearly equal measure; and in the autumn seasons, copepods prevailed. Among rotifers, species of the genus Brachionus (Pallas, 1766) prevailed, along with Euchlanis dilatata (Ehrenberg, 1832); among cladocerans, dominant species were Bosmina longirostris (O.F. Müller, 1785) and Chydorus sphaericus (O.F. Müller, 1776); among copepods, brackish-water species Calanipeda aquaedulcis (Kritszagin, 1873), Eurytemora affinis (Poppe, 1880), and Eurytemora velox (Lilljeborg, 1853) prevailed. The list of zooplankton species composition is presented; it comprises 75 taxa of holoplankton and 8 taxa of meroplankton. Based on the data from species composition of zooplankton community, it has been concluded that the ecological state of the Lower Don waters remains stable for the several recent decades.
Keywords: Lower Don, zooplankton community, species composition, dominant species
Assessment of seasonal variations at the stages of production and destruction succession in the microplankton off the Crimean Coast and deep waters of the Northern Black Sea on the basis of ATP and chlorophyll α analysis
Sysoev A.A., Sysoeva I.V.
Abstract. Based on the data collected during scientific expeditions of RV “Professor Vodyanitsky” in January, April, October 2016 and July 2017, spatial and temporal changes in distribution of microplankton ATP and chlorophyll α as indicators of metabolically active biomass and its photoautotrophic part, respectively, were analyzed. The heterotrophic-photoautotrophic index (HPI) was calculated from ratios of these biochemical parameters and used to assess the stages of production and destruction succession of microplankton community over these seasons. In the investigated area, the sites, which most often demonstrate sharp differen ces in biochemical parameters of microplankton from the general background, can be considered anomalous and subjected to anthropogenic impact, mainly associated with household and industrial effluents. In general, upon comparison of the distribution of the metabolically active biomass and its production part in the specified seasons the similarity in the values manifested itself in the shallow coastal waters of Crimea: low values for the waters near the western part of the peninsula were assessed to be oligo-mesotrophic; increased values for the waters adjacent to the Kerch Strait in the east were found to be meso-eutrophic. Based on the HPI values, the situation, most promising in terms of development of microplankton biomass and increase in water productivity was observed in the investigated area in autumn. Quite possibly, it is one of the key factors affecting seasonal migration of some fish species from the Azov Sea to the Black Sea in the autumn-winter season.
Keywords: Black Sea, Crimea, coastal waters, microplankton, ATP, chlorophyll α, heterotrophic-photoautotrophic index, seasonal variations
Ichthyofauna of Marine and Inland Water Bodies
Current state of aquatic biological resources in the Balkhash-Ili Basin
Kassymbekov Ye.B., Pazylbekov M.Zh.
Abstract. The maternal composition of ichthyofauna in the Balkhash-Ili Basin was extremely poor, and consisted of several native species that belonged to the Nagorno-Asian faunistic complex. As early as 1885, the introduction of the European carp into the basin was recommended, and it was carried out at the beginning of the 20th century. Large-scale fish introductions were conducted between 1964 and 1988. Formation of a significant commercial stock of common bream, zander (pike perch) and asp, which became the main commercial fish species of the basin, was a positive effect associated with this period. After implementation of a series of acclimatization programs, the modern composition of the fauna in the basin was formed, comprising both introduced and native species. This article discusses the current state of aquatic biological resources in the Balkhash-Ili Basin. The data on the state of fish resources, species diversity of fish communities, fish population dynamics, and the commercial fish stock in the Qapshaghay Reservoir and the Ili River are presented. The main reasons for the decrease in the ichthyofauna natural reserves are determined: regulation of the rivers with spawning grounds, unfavourable hydrological regime, unsustainable fishing, and poaching pressure. To improve the state of natural fish stocks, it is necessary to increase the efficiency of their reproduction and to implement measures on restoration and rational exploitation of the aquatic biological resources in the Balkash-Ili Basin.
Keywords: Balkhash-Ili Basin, Ili River, Qapshaghay Reservoir, ichthyofauna, population dynamics, abundance, native species, introduced species
Fisheries and Processing of Aquatic Bioresources
On the role of temperature as a factor influencing the behavior of the European sprat and the efficiency of its fishing
Panov B.N., Spiridonova E.O., Piatinskii M.M., Stytsyuk D.R.
Abstract. This paper presents the results of monitoring of the European sprat fishing, carried out in April– October of 2019, which make it possible to characterize specific features of the variability of sea surface temperature (SST), both seasonal and synoptic, as well as the behavior of the European sprat and the efficiency of its fishing. For this purpose, the daily SST maps of the Black and Azov Seas, created in the Hydrometeorological Center of Russia and based on the NCDC/NOAA (ESIMO Operational Module) data, and daily fishing information of the FSBI “Centre of Fishery Monitoring and Communications” have been used. The trends in the fish ing pressure (daily catch) of each vessel and the average daily fishing pressure for the vessels in general have been investigated, and the information about the operation area of each vessel and SST in the main fishing areas has been collected. To study the changes of these parameters with time, mainly the methods of graphical analysis have been used. It is shown that the first period of relatively high density of sprat aggregations was noted at winter water temperatures, the second one coincided with a steady increase in SST, and the third period fell on the stabilization of summer temperature conditions. During this period, signs of a direct dependence of the sprat fishing efficiency on SST were revealed for the Caucasian fishing area and the South Coast of the Crimea; along the western coast of the Crimea, an inverse relation between them was found out. Effective fishing ceased after the SST decreased below 23.5 °C.
Keywords: European sprat, fishing, monitoring, sea surface temperature, synoptic variability, fishing efficiency
Informational Messages
On the state monitoring service for aquatic biological resources and their habitat
Strelchenko O.V., Polin A.A.
Abstract. The purpose of the State Monitoring Service for Aquatic Biological Resources and Their Habitat is the preservation of aquatic biological resources (ABR) and their habitat. The Service has six main goals:
1. monitoring of the state of water bodies of fishery importance, including for the purpose of forecasting and preventing the mortality of ABR; 2. collection of information on water bodies for the purpose of attaining their fishery characteristics and making proposals on their fishery classification; 3. the study of the species composition of ABR while conducting various types of fishing; 4. monitoring of fish migrations through fish-passage facilities; scientific support for the practices of artificial reproduction of valuable and highly valuable species of ABR; interaction with representatives of executive authorities in the field of ABR preservation. The structure of the Service is represented by two groups, comprising 13 monitoring posts, namely: the Taganrog, Azov, Veselovsky, Kamensk, Konstantinovsk, Semikarakorsk, Pre-Caucasian, Yeisk, Primorsko-Akhtarsk, Temryuk, Black Sea, East Crimean, and Sevastopol posts. The water bodies, located in the area of seven constituent territories of the Russian Federation (Rostov Region, Krasnodar Krai, Stavropol Krai, the Karachay-Cherkess Republic, the Republic of Adygea, the Republic of Crimea and Sevastopol), are responsibility of the Service.
Keywords: Azov-Вlack Sea Fishery Basin, state monitoring, aquatic biological resources, habitat, water bodies
Experience in organizing the remote collaboration of hydrobiologists and creating a database of digital images of plankton and benthos
Afanasyev D.F., Bondarev S.V., Khrenkin D.V., Zhivoglyadova L.A.
Abstract. A database of digital images of common species of phytoplankton, zooplankton, phytobenthos and zoobenthos of the Black and Azov Seas is being created in the Laboratory of Hydrobiology of the Azov-Black Sea Branch of “VNIRO” (“AzNIIRKH”). No ecological databases focused on the species from the Black and Azov Seas, as well as from the freshwater bodies and streams of the Southern Russia are currently known to exist. International databases include some taxa of plankton and benthos inhabiting the Black and Azov Seas. Due to the territorial disunity of the researchers from the Azov-Black Sea Branch of “VNIRO” (“AzNIIRKH”), remote interaction was organized between those engaged in the processing of phytoplankton, zooplankton, zoobenthos and phytobenthos samples. The task of identifying species is one of the most challenging and time- consuming in hydrobiological research; its solution requires from a specialist not only skills and a certain level of experience, but also continuous training in the relevant field of research. The creation of a database of digital photographic images will speed up the process of species determination and, prospectively, will allow automated processing of hydrobiological samples. A system of remote online consultations between the scientists, which applies the peer-to-peer networking technology, has been tested and is being actively implemented. Operational data exchange and online consultations make it possible to efficiently solve problems, as well as train young specialists via remote access.
Keywords: hydrobiology, databases, digital images, phytoplankton, zooplankton, zoobenthos, phytobenthos